Consider the following hypothesis test

Ho: >= 20

Ha: < 20

A sample of 50 provided a sample mean of 19.4. The population standard deviation is 2.

a- compute the value of the test statistic? I got 2.12

b- what is the p-value? is it .017 or is it .9830 because it is upper tail

c- using alpha=.05, what is your conclusion?

d- what is the rejection rule using critical value?